This invention pertains to the field of integrated optics and photonics. Applications include optical and electronic communications, cable television, and waveguide sensing.
Integrated-optic devices are made according to photo lithographic and micro fabrication techniques. This makes possible mass production, in the same way as for electrical integrated circuits. The most common electro-optic substrate materials for integrated-optic devices are the semiconductors gallium arsenide (GaAs) and indium phosphide (InP) and lithium niobate, a ferroelectric insulating crystal. Lithium niobate is a strong, easily polished nonhydroscopic crystal, with a good electro-optic coefficient. It also has low optical transmission loss.
The emerging field of integrated optical systems has generated a number of components analogous to those employed in electronic circuits. For example, there are devices for performing beam-splitting and/or recombination functions such as those shown in U.S. Pat. No. 5,410,625. There are devices for performing optical mixing, such as those shown in U.S. Pat. No. 5,475,776. And there are devices for performing signal routing, such as those shown in U.S. Pat. No. 5,428,698.
Wavelength division (de)multiplexers for 1.3 .mu.m and 1.5 .mu.m are required in the field of fiber optic communications to take advantage of embedded fiber optic systems at 1.3 .mu.m and proceed with deployment of the lower loss 1.5 .mu.m systems. Commercially available 2-wavelength demultiplexing devices rely on bulk optical filters and therefore suffer high insertion loss and are not mass reproduceable. The use of self-imaging to perform wavelength division (de)multiplexing operations would yield several advantages over currently available wavelength division (de)multiplexers, such as: (a) low insertion loss, (b) low polarization crosstalk, (c) good wavelength separation, (d) ease in manufacture, and (e) environmental insensitivity.